1. Field of the Invention
This invention relates to the treatment of aquaculture pond water to reduce organic waste, ammonia, and disease pressure in a water livestock application.
2. Description of Related Art
Aquaculture refers to the raising of aquatic species that are used as a human or animal food source. The technique applies some types of control to the natural environment of the raised species to improve overall harvests. This can include the artificial hatching of species to increase the commercial harvest of animals in the wild, hatching and raising of the species in enclosed ponds, and the hatching and raising of species in tidally drained enclosed areas adjacent to the shoreline. Problems associated with this process include: pollution that is discharged from the raising facility and will deteriorate the water quality around; loss of product due to deteriorated water quality in the raising facility; and increased disease pressures associated with pathogenic microorganisms in the raising facility. Such problems may be identified through testing or monitoring a variety of parameters, including pH, conductivity, ammonia, nitrate, phosphate and alkalinity. Conductivity is an indicator of salt content, amounts greater than 1200 ppm is no longer considered fresh water; an ideal amount is 700 ppm and range of 300-1200 ppm. Ammonia levels measure the amount of available oxygen for fish. High levels of ammonia block oxygen transfer in fish from gills to the blood; however it is also a product of their metabolic waste. While ammonia from fish waste is often not concentrated enough to be toxic itself, fish farmers must closely monitor ammonia levels due to the high concentration of fish per pond. Oxygen is consumed by nitrifying bacteria in the pond which break down the toxic ammonia to a non-toxic form; however, this massive use of oxygen reduces the oxygen available for uptake by fish. Ammonia levels >1 ppm are considered toxic for fish life. Additionally, nitrate levels are examined to determine the amount of plant fertilizer in the water. Nitrate is highly leachable from the surrounding soil and can be harmful to small children and pregnant women. Nitrate becomes nitrite in the GI tract and interacts with the blood's ability to carry oxygen. Max contamination level for nitrate is 10 ppm. Alkalinity is the measure of a pond's or lake's ability to neutralize acid without a change in pH. Alkalinity will decrease over time due to bacteria; however an ideal level is 100 ppm with acceptable range of 50-200 ppm. Phosphate found in ponds and lakes is largely from human and animal waste. Fertilizer run-off is a major source of phosphate found in golf course and decorative ponds. Elevated levels cause an increased rate of eutrophication which in turn increases sludge production. Moderation levels of phosphate can stimulate plant growth causing an increase in algae production; levels of >0.1 ppm is an indication of accelerated plant growth and is considered outside acceptable levels.
Current technologies to address these problems include bioremediation, antibiotics, and chemical additives. Typical bioremediation technologies include the application of supplemental bacteria to the water to enhance the microbiological activities to improve the water quality. It is also known to use nitrifiers to enhance the nitrification process to convert the toxic ammonia into non-toxic nitrate. Chemical additives are added to improve the water quality and aid the microbiological activities by providing extra nutrients and alkalinity. Antibiotics are added to inhibit the growth of the pathogenic microorganisms. Problems associated with the current technologies include high cost and poor water quality improvement performance with the inactive supplemental bacteria, low nitrification activities due to the existence of organic waste and lack of nitrifier growing sites, bioaccumulation of antibiotics in the raised aquatic species.